Which trait of this sloth gave name to its taxonomic family?

two tails

split tongue

two fingers

doubled ears

The living sloths belong to one of two fam­i­lies, known as the Mega­lony­chi­dae ("t­wo-­toed" sloths) and the Brady­po­di­dae (three­-­toed sloths). The name should in fact be rather "two fin­gered" or "three fin­gered" as all living sloths have in fact three toes in their feet, and differ by the number of fingers in their arms (which were con­sid­ered front feed in the past).